Differential Diagnosis: Definition and Examples

What is a differential diagnosis?

Differential diagnosis is the process by which a healthcare provider distinguishes between two or more conditions that share similar symptoms. It involves sorting through the patient's characteristics in the form of signs, symptoms, patient history, and test results to determine a definitive/disease diagnosis.

One of the most essential tasks by healthcare providers is diagnosis (World Health Organization, 2016). Differential diagnosis is then the foundation for a clear and confident diagnosis. Its goal is not simply to identify a single possible condition but to compile a comprehensive list of potential diagnoses that could cause the patient's symptoms.

Here are some reasons a differential diagnosis is essential when providing care:

• Quality care: A thorough differential diagnosis ensures accurate treatment, prioritizing patient well-being and precise care.
• Multiple matches: Many symptoms can point to several different conditions. A fever, for instance, could be a sign of the flu, an infection, or even an autoimmune disorder. A differential diagnosis helps you sort through these possibilities systematically.
• Accuracy matters: Ruling out less likely causes early on saves valuable time and prevents unnecessary tests as you diagnose a patient. It ensures you're focusing your diagnostic efforts on the most relevant avenues.
• Prioritization: A differential diagnosis allows you to prioritize the most serious or urgent treatment conditions that may require immediate medical attention, ensuring a patient receives timely and appropriate care.

When to conduct a differential diagnosis?

A differential diagnosis is conducted when symptoms match more than one condition, and additional tests are necessary before making an accurate diagnosis. Tests will narrow down potential conditions on your healthcare provider’s differential diagnosis list.

The following are some key scenarios where performing a differential diagnosis is essential:

Complex symptoms

When a patient's symptoms are not clearly indicative of a single condition and could be linked to various diseases or disorders, a differential diagnosis is necessary to pinpoint the underlying cause accurately. This can happen in certain conditions where multiple body systems are involved or when the symptoms are nonspecific and could be attributed to various diseases.

Unclear diagnosis

A differential diagnosis helps explore other potential conditions when initial assessments or test results don't provide a definitive diagnosis. Revisiting and expanding the list ensures no potential diagnosis is overlooked, leading to a more accurate and effective care plan.

Uncommon presentations

When a patient's symptoms present atypical or unusual, we need to conduct a differential diagnosis to explore less common but possible explanations for the observed signs. A differential diagnosis prompts a broader look at various possibilities, even those that might seem less likely at first glance.

Multiple coexisting conditions

When a patient has multiple medical conditions simultaneously, a differential diagnosis is essential to differentiate between symptoms caused by each condition and tailor treatment accordingly. A patient's medical background and family history can be a valuable clue. For instance, if they have a history of allergies, a persistent cough might require a different approach than for someone with no allergies.

What is the differential diagnostic process?

A differential diagnosis is more than just a list of possibilities; rather, it is a structured method to identify the cause of a patient's symptoms and guide accurate treatment.

Here are the key steps involved in the differential diagnosis process:

Step 1: Gathering patient information

Begin by collecting a detailed medical history from the patient, including symptoms, duration, severity, and any relevant past medical conditions. This can help understand the patient's background and possible risk factors leading to specific conditions.

Step 2: Conducting a physical examination

Perform a thorough physical exam to assess the patient's vital signs, look for specific physical signs related to the symptoms, if any, check vital signs such as heart rate and blood pressure, and gather additional clues for a correct diagnosis. This helps guide relevant diagnostic methods and rule out physiological causes in cases of psychological disorders.

Step 3: Creating a differential diagnosis

Compile a list of possible conditions that could explain the patient's symptoms, considering both common and rare diseases that match the clinical presentation.

Step 4: Ordering diagnostic tests

Based on the differential diagnosis, appropriate tests such as blood, laboratory, and imaging tests should be ordered. We can also conduct additional medical tests and assessment methods to gather objective data and narrow down potential diagnoses.

Step 5: Evaluating and prioritizing diagnoses

Evaluate each potential diagnosis based on the patient's history, physical findings, and test results. Prioritize the most likely conditions while ruling out less probable ones.

Step 6: Reaching a final diagnosis

Through a process of elimination and careful evaluation of all diagnostic findings, arrive at a final diagnosis that best explains the patient's symptoms and guides appropriate treatment.

Differential diagnosis examples

Here are some examples of common symptoms presented and the possible differential diagnoses associated with them:

Chest pain

Chest pain is a symptom with potentially life-threatening causes, demanding an immediate and systematic approach to differential diagnosis:

• Myocardial infarction: Caused by the blockage of blood flow to the heart muscle.
• Angina pectoris: Results from reduced blood flow to the heart, similar to myocardial infarction but often transient.
• Aortic dissection: Involves the tearing of the aorta's inner layer, requiring swift diagnosis and intervention.
• Pulmonary embolism: A blockage in one of the pulmonary arteries in the lungs.

Headache

Headaches are common, with causes that range from benign to needing urgent care.

• Migraine: Characterized by recurrent headaches that are often debilitating.
• Tension-type headache: Features a band-like pain and is the most common type of headache.
• Cluster headaches: Known for severe, burning pain around one eye, occurring in clusters.
• Brain tumor: While less common, headaches due to tumors are a critical consideration.

Abdominal pain

Abdominal pain can indicate a myriad of conditions requiring careful diagnosis.

• Appendicitis: An inflamed appendix, often requiring surgical removal.
• Irritable bowel syndrome (IBS): A common condition affecting the large intestine, causing cramping, bloating, and other symptoms.
• Peptic ulcers: Open sores that develop on the inner lining of the stomach and small intestine.
• Diverticulitis: Inflammation or infection in one or more small pouches in the digestive tract.

Shortness of breath

Evaluating shortness of breath requires considering a variety of pulmonary and non-pulmonary causes.

• Asthma: A common pulmonary disorder that narrows and inflames the airways.
• Heart failure: A non-pulmonary condition where the heart doesn't pump blood as well as it should.
• Chronic obstructive pulmonary disease (COPD): A group of progressive lung diseases, including emphysema and chronic bronchitis.
• Anemia: A condition in which you lack enough healthy red blood cells to carry adequate oxygen to your body's tissues, causing fatigue and shortness of breath.

Joint pain

Joint pain can stem from a variety of rheumatologic and non-rheumatologic conditions.

• Rheumatoid arthritis (RA): An autoimmune disorder that affects the lining of the joints.
• Osteoarthritis: The wear and tear of joint cartilage due to aging or injury.
• Lupus: An autoimmune disease that can cause inflammation in many different body systems, including the joints.
• Gout: A form of arthritis characterized by severe pain, redness, and tenderness in joints caused by the crystallization of uric acid.

Mood disturbances

Mood disturbances span a spectrum of psychiatric conditions that often require careful differentiation.

• Major depressive disorder (MDD): Exhibits persistent and pervasive low mood.
• Bipolar disorder: Features episodes of both low (depressive) and high (manic) moods.
• Borderline personality disorder: This can include affective instability, resulting in rapidly fluctuating moods.
• Hormonal imbalances: Conditions like hypothyroidism or menopause can result in mood symptoms that may mimic psychiatric disorders.

It is important to note that each differential diagnosis will differ based on the patient's medical history and clinical presentation.

Reference

World Health Organization. (2016, December 13). Technical series on safer primary care: Diagnostic errors. https://www.who.int/publications/i/item/9789241511636